Investigations of the biochemical and pharmacological properties of subpopulations of opiate receptors will be carried out. These studies will utilize a variety of enzyme and reagent treatments in addition to new and unique opiate-like drugs. Attempts will be made to correlate receptor subpopulations with pharmacological actions of opiates and the opioid peptides in vivo. Further studies on the mechanisms of action of several irreversible opiate agonists and antagonists will also be initiated.